Articles such as hard disks, semiconductor wafers, delicate optics, etc., often must be precisely cleaned in order to remove contaminants, either during or after a process for manufacturing the articles. For example, resist strip and residue clean typically are needed between etch, implant and deposition steps in IC fabrication processes. Conventional dry-type strip/clean sequences typically use plasma to ash resist and wet chemicals to clean residues. Resist stripping is typically carried out using dry plasma ashing. Conventional O2 plasma ashing at high temperature tends to leave polymeric residues that require acids and/or organic solvents for removal. Wet chemistries generally are not desirable due to non-uniformities, selectivity to exposed layers and incomplete resist removal because of mass transport and surface tension associated with the solutions. A variety of alternative cleaning methods have been employed with varying degrees of success. Certain of such methods that have been attempted involve imparting carbon dioxide snow onto the article to be cleaned.
An example of such a conventional carbon dioxide cleaning system is described in U.S. Pat. No. 5,766,061. As a general/summary description of this system, a conveyor transports a wafer-carrying cassette to be cleaned in an enclosure. Jet spray nozzles generate carbon dioxide spray that cleans the wafers. While methods such as described in this patent provide a certain level of cleaning efficacy, improved methods for cleaning a variety of articles are still very much in demand. In addition, conventional jet spray nozzle approaches, while effective in some applications, generally fail in the majority of applications where the bonding between the surface of the wafer and the contamination on the wafer are strong and require chemical reaction, such as plasma, as well as a physical cleaning mechanism for adequate de-contamination and removal of residues, etc.